1. Field of the Invention
The present invention relates generally to wireless data networks and, more particularly, to a method and apparatus for converging local area and wide area wireless data networks.
2. Description of Related Art
Wireless data technologies are used to provide Internet and other network access to mobile client devices such as, e.g., laptops, personal digital assistants (PDAs), and smartphones. With the growing popularity of the Internet and the increasing mobility demands from end users, there has recently been increased interest and activity in wireless data networks. Some wireless data technologies are designed to support wide area coverage, while others are designed for the local area.
In the wide area, cellular operators such as AT&T are presently deploying high-speed packet based wireless wide area networks (WANs). Older wide area wireless data technologies have used Cellular Digital Packet Data (CDPD) and circuit switched data. While these older technologies offer coverage over a large area, they are limited in the bit rates offered (˜20 kbps) and accordingly somewhat restrict the types of applications that could be accessed. With the advent of higher-speed technologies such as General Packet Radio Service (GPRS) and Wideband Code Division Multiple Access (WCDMA), cellular operators are now building out wireless data networks that will provide moderately high speed (˜100 kbps) access to the Internet. These networks are based on the so-called 2.5 G wireless data technologies, such as GPRS and 1XRTT. It is expected that these wireless data technologies will provide convenient access to the Internet over a large coverage area, with each base station in the network typically covering up to several miles. Due the relatively higher bit rate, various applications are now envisioned that will extend the reach of the Internet to the wireless world. Users are expected to access these networks through various client devices such as next-generation smart phones as well as PDAs and laptops with 2.5 G network interface cards.
In the local area, enterprises and universities are now deploying wireless local area networks (LANs) based on the IEEE 802.11b standard. Users with client devices such as laptops and PDAs use an 802.11 network interface card that enables them to access the Internet without having to be attached to a desktop. The current 802.11 technology allows access at speeds up to 11 Mbps over a range of several hundred feet. In addition to replacing traditional Ethernet-based local area networks, these wireless LANs are now also being deployed in novel settings. Of special interest is the increasing deployment of these 802.11 based networks in public spaces and hot spots such as, e.g., airports, convention centers, hotels, and even local coffee shops. These hotspots promise to provide localized wireless access at fast speeds. The hotspots are typically managed by local wireless Internet service providers (ISPs) such as, e.g., Wayport or by wireless LAN infrastructure integrators such as, e.g., Concourse Communications.
Advantages of WANs include wide coverage and “always on” access. These networks typically cover large areas of several miles. Due to the packet-based nature and the large coverage areas of these networks, 2.5 G enables data access all the time.
Disadvantages of wide area networks include limited bit rate and expensive equipment. Compared with the data speeds of several Mbps typically available in enterprises today as well as the 11 Mbps rate offered by 802.11b, the data rates achievable with 2.5 G are quite limited. For example, most 2.5 G networks will offer data rates of only up to 144 kbps. Also, the equipment needed to deploy the 2.5 G networks is quite expensive, in line with costs of traditional carrier-scale switching systems. A base station, e.g., can typically cost several hundred thousand dollars.
Advantages of the 802.11 LANs include a high data rate and inexpensive equipment. Relative to the 2.5 G networks, the wireless 802.11 LANs can support peak data rates of up to 11 Mbps in current generation technology. Further enhancements to this technology can support upto 54 Mbps data rates as well (802.11g and 802.11a). The cost of 802.11 equipment is also quite reasonable, and is typically a couple of orders of magnitude below that of the WAN networks. Also, the 802.11 networks operate in the unlicensed band. As a result, there are no spectrum acquisition costs associated with wireless LAN deployments.
Disadvantages of 802.11 based networks are limited coverage and no “always on” access. The coverage of each 802.11 base station (called access point) is typically limited to 150-200 ft. Also, since the coverage areas are limited, it is prohibitively expensive to deploy 802.11 based networks over large areas. As a result, it is not practical to obtain the same benefit of ‘always on’ access for these networks.